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WHO/SDE/PHE/01.1 English only Limited

Depleted

Sources, Exposure and Health Effects

Department of Protection of the Human Environment World Health Organization

April 2001 The illustration of the cover page is extracted from Rescue Mission: Planet Earth, ã Peace Child International 1994; used by permission.

ã World Health Organization 2001

This document is not issued to the general public and all rights are reserved by the World Health Organization. The document may not be reviewed, abstracted, quoted, reproduced or translated, in part or in whole, without the prior written permission of WHO. No part of this document may be stored in a retrieval system or transmitted in any form or by any means – electronic, mechanical or other without the prior written permission of WHO.

The views expressed in documents by named authors are solely the responsibility of those authors. Preface

Depleted uranium (DU) has been used in medical and industrial applications for decades but only since its use in military conflicts in the Gulf and the Balkans has public concern been raised about potential health consequences from exposure to it. Concerns have been particularly for peacekeeping forces, humanitarian workers and local populations living and working in areas contaminated by DU following conflict.

There has been a large amount of research on the health consequences to workers in the and milling of uranium, and on its use in , that enables a reasonable assessment of its impact on human health1. Since DU acts chemically in the same way as uranium, and the radiological toxicity is somewhat less than uranium, this research can be used to evaluate health risks from ingestion, inhalation and contact with DU.

In late 1999, the WHO Department on the Protection of the Human Environment (PHE) recognized the need for an independent review of the scientific literature from which health risks could be assessed from various DU exposure situations. Professor Barry Smith from the British Geological Survey, UK, was contracted to prepare the draft from the literature that would be subject to rigorous scientific review. The format of the review was to be modelled on monographs in the WHO criteria series.

An ad hoc review and oversight group of WHO staff members was formed and coordinated by Dr . Participants and contributors to the review included: Drs Ala Alwan, Antero Aitio, Jamie Bartram, Keith Baverstock, Elisabeth Cardis, Carlos Corvalan, Marilyn Fingerhut, Yoshikazu Hayashi, Richard Helmer, Jenny Pronczuk, Colin Roy, Dieter Schwela, Gennadi Souchkevich and Maged Younes.

The National Radiological Protection Board (NRPB) in the United Kingdom, a WHO Collaborating Centre on ionizing and non-ionizing , provided many contributions relating to the radiological toxicity of DU. These contributions were provided by Dr Neil Stradling and other staff identified below.

The National Institute of Occupational Safety and Health (NIOSH) of the Center for Disease Control (CDC) in the USA, a WHO Collaborating Centre on occupational health, provided contributions mainly related to DU occupational health and safety requirements, protective measures and health monitoring. These contributions were provided by Dr Jim Neton and other staff identified below. The Centre for Health Promotion and Preventative (CHPPM) in the USA, provided contributions relating mainly to DU applications, radiological toxicity and medical care of people exposed to DU. These contributions were provided by Dr Mark Melanson and other staff identified below.

The International Atomic Agency (IAEA) provided contributions on the effects of and internationally recognized standards. These contributions were provided by Dr Carol Robinson and Dr Tiberio Cabianca.

Included in these reviewers and contributors are members of the International Commission on Radiological Protection (ICRP) an NGO in formal relations with WHO.

1 The Government of has reported increases in , congenital abnormalities and other diseases following the Gulf war in 1991, but there are no published results for review. WHO is working with the Government of Iraq to prepare studies to investigate this situation. i There have been a large number of contributors to this monograph, and it has been reviewed widely. In addition to the internal WHO review group, contributors and reviewers are listed below in alphabetical order:

· AC-Laboratorium Spiez, : Dr Ernst Schmid · ATSDR, USA: Dr Sam Keith · Batelle Pacific Northwest Laboratoies, USA: Dr Tom Tenforde · CHPPM, USA: Drs Dave Alberth, Marianne Cloeren, Richard Kramp, Gordon Lodde, Mark Melanson, Laurie Roszell, Colleen Weese · Electric Power Research Institute, USA: Dr Leeka Kheifets · Hopital Cantonal Universitaire, Division de médecine nucléaire, Geneva: Dr Albert Donath · IAEA: Drs Tiberio Cabianca, Carol Robinson · Karolinska Institute, Sweden: Dr Lennart Dock · NIOSH, USA: Drs Heinz Ahlers, Bonnie Malit, Jim Neton, Michael Ottlinger, Paul Schulte, Rosemary Sokas · NRPB, UK: Drs Mike Bailey, George Etherington, Alan Hodgson, Colin Muirhead, Alan Phipps, Ed Rance, Jennifer Smith, Neil Stradling · SCK·CEN Studiecentrum voor Kernenergie Centre d'étude de l'Energie Nucléaire, Belgian Nuclear Research Centre : Dr Christian Hurtgen · Swedish Institute, Stockholm: Drs Gustav Akerblom, Jan Olof Snihs · UNEP, Balkans Unit: Mr Henrik Slotte

The monograph was technically edited by Professor Barry Smith and language edited by Audrey Jackson, both from the British Geological Survey, UK. WHO acknowledges, with sincere gratitude, the contributions of all the authors and reviewers of this important monograph. In addition, WHO also acknowledges with thanks the photographs related to DU provided by IAEA, NIOSH and ATSDR.

WHO has and will continue to work with the United Nations Environment Programme (UNEP), the International Atomic Energy Agency (IAEA) and other UN agencies, Collaborating Centres and NGOs to advance our knowledge about exposure to DU and other environmental risk factors that could have consequences for health. Such programmes are aimed at providing essential information to member states and assisting national health services to deal with chemical, physical and biological risk factors in their environment.

ii Executive Summary

This scientific review on is part of the World Health Organization's (WHO's) ongoing process of assessment of possible health effects of exposure to chemical, physical and biological agents. Concerns about possible health consequences to populations residing in conflict areas where depleted uranium munitions were used have raised many important environmental health questions that are addressed in this monograph.

Purpose and scope

The main purpose of the monograph is to examine health risks that could arise from exposure to depleted uranium. The monograph is intended to be a desk reference providing useful information and recommendations to WHO Member States so that they may deal appropriately with the issue of depleted uranium and human health.

Information is given on sources of depleted uranium exposure, the likely routes of acute and chronic intake, the potential health risks from both the radiological and chemical toxicity standpoints and future research needs. Several ways of uptake of compounds with widely different solubility characteristics are also considered.

Information about uranium is used extensively because it behaves in the body the same way as depleted uranium.

Uranium and depleted uranium

Uranium is a naturally occurring, ubiquitous, heavy metal found in various chemical forms in all soils, rocks, seas and oceans. It is also present in drinking water and food. On average, approximately 90 µg (micrograms) of uranium exist in the human body from normal intakes of water, food and air; approximately 66% is found in the skeleton, 16% in the liver, 8% in the kidneys and 10% in other tissues.

Natural uranium consists of a mixture of three radioactive which are identified by the mass numbers 238U(99.27% by mass), 235U(0.72%) and 234U(0.0054%).

Uranium is used primarily in nuclear power plants; most reactors require uranium in which the 235U content is enriched from 0.72% to about 3%. The uranium remaining after removal of the enriched fraction is referred to as depleted uranium. Depleted uranium typically contains about 99.8% 238U, 0.2% 235U and 0.0006% 234U by mass.

For the same mass, depleted uranium has about 60% of the radioactivity of uranium.

Depleted uranium may also result from the reprocessing of spent fuel. Under these conditions another uranium , 236U may be present together with very small amounts of the transuranic elements , and and the fission product technetium-99. The increase in the radiation dose from the trace amounts of these additional elements is less than 1%. This is insignificant with respect to both chemical and radiological toxicity.

iii Uses of depleted uranium

Depleted uranium has a number of peaceful applications: counterweights or ballast in aircraft, radiation shields in medical equipment used for and containers for the transport of radioactive materials.

Due to its high density, which is about twice that of , and other physical properties, depleted uranium is used in munitions designed to penetrate armour plate. It also reinforces military vehicles, such as tanks.

Exposure and exposure pathways

Individuals can be exposed to depleted uranium in the same way they are routinely exposed to natural uranium, i.e. by inhalation, ingestion and dermal contact (including injury by embedded fragments).

Inhalation is the most likely route of intake during or following the use of depleted uranium munitions in conflict or when depleted uranium in the environment is re- suspended in the atmosphere by wind or other forms of disturbance. Accidental inhalation may also occur as a consequence of a fire in a depleted uranium storage facility, an aircraft crash or the decontamination of vehicles from within or near conflict areas.

Ingestion could occur in large sections of the population if their drinking water or food became contaminated with depleted uranium. In addition, the ingestion of soil by children is also considered a potentially important pathway.

Dermal contact is considered a relatively unimportant type of exposure since little of the depleted uranium will pass across the skin into the blood. However, depleted uranium could enter the systemic circulation through open wounds or from embedded depleted uranium fragments.

Body retention

Most (>95%) uranium entering the body is not absorbed, but is eliminated via the faeces. Of the uranium that is absorbed into the blood, approximately 67% will be filtered by the kidney and excreted in the urine in 24 hours.

Typically between 0.2 and 2% of the uranium in food and water is absorbed by the gastrointestinal tract. Soluble uranium compounds are more readily absorbed than those which are insoluble.

Health effects

Potentially depleted uranium has both chemical and radiological toxicity with the two important target organs being the kidneys and the lungs. Health consequences are determined by the physical and chemical nature of the depleted uranium to which an individual is exposed, and to the level and duration of exposure.

Long-term studies of workers exposed to uranium have reported some impairment of kidney function depending on the level of exposure. However, there is also some evidence that this impairment may be transient and that kidney function returns to normal once the source of excessive uranium exposure has been removed. iv Insoluble inhaled uranium particles, 1-10 µm in size, tend to be retained in the lung and may lead to damage of the lung and even lung if a high enough radiation dose results over a prolonged period.

Direct contact of depleted uranium metal with the skin, even for several weeks, is unlikely to produce radiation-induced (superficial of the skin) or other short term effects. Follow-up studies of veterans with embedded fragments in the tissue have shown detectable levels of depleted uranium in the urine, but without apparent health consequences. The radiation dose to military personnel within an armoured vehicle is very unlikely to exceed the average annual external dose from natural from all sources.

Guidance on chemical toxicity and radiological dose

The monograph gives for the different types of exposure the tolerable intake, an estimate of the intake of a substance that can occur over a lifetime without appreciable health risk. These tolerable intakes are applicable to long term exposure. Single and short term exposures to higher levels may be tolerated without adverse effects but quantitative information is not available to assess how much the long term tolerable intake values may be temporarily exceeded without risk.

The general public’s ingestion of soluble uranium compounds should not exceed the tolerable intake of 0.5 µg per kg of body weight per day. Insoluble uranium compounds are markedly less toxic to the kidneys, and a tolerable intake of 5 µg per kg of body weight per day is applicable.

Inhalation of soluble or insoluble depleted uranium compounds by the public should not exceed 1 µg/m3 in the respirable fraction. This limit is derived from renal toxicity for soluble uranium compounds, and from for insoluble uranium compounds.

Excessive worker exposure to depleted uranium via ingestion is unlikely in workplaces where occupational health measures are in place.

Occupational exposure to soluble and insoluble uranium compounds, as an 8-hour time weighted average should not exceed 0.05 mg/m3. This limit is also based both on chemical effects and radiation exposure.

Radiation dose limits

Radiation dose limits are prescribed for exposures above natural background levels.

For occupational exposure, the effective dose should not exceed 20 millisieverts (mSv) per year averaged over five consecutive years, or an effective dose of 50 mSv in any single year. The to the extremities (hands and feet) or the skin should not exceed 500 mSv in a year.

For exposure of the general public the effective dose should not exceed 1 mSv in a year; in special circumstances, the effective dose can be limited to 5 mSv in a single year provided that the average dose over five consecutive years does not exceed 1 mSv per year. The equivalent dose to the skin should not exceed 50 mSv in a year. v Assessment of intake and treatment

For the general population it is unlikely that the exposure to depleted uranium will significantly exceed the normal background uranium levels. When there is a good reason to believe that an exceptional exposure has taken place, the best way to verify this is to measure uranium in the urine.

The intake of depleted uranium can be determined from the amounts excreted daily in urine. depleted uranium levels are determined using sensitive mass spectrometric techniques; in such circumstances it should be possible to assess doses at the mSv level.

Faecal monitoring can give useful information on intake if samples are collected soon after exposure.

External of the chest is of limited application because it requires the use of specialist facilities, and measurements need to be made soon after exposure for the purpose of dose assessment. Even under optimal conditions the minimum doses that can be assessed are in the tens of mSv.

There is no suitable treatment for highly exposed individuals that can be used to appreciably reduce the systemic content of depleted uranium when the time between exposure and treatment exceeds a few hours. Patients should be treated based on the symptoms observed.

Conclusions: Environment

Only military use of depleted uranium is likely to have any significant impact on environmental levels. Measurements of depleted uranium at sites where depleted uranium munitions were used indicate only localized (within a few tens of metres of the impact site) contamination at the ground surface. However, in some instances the levels of contamination in food and ground water could rise after some years and should be monitored and appropriate measures taken where there is a reasonable possibility of significant quantities of depleted uranium entering the food chain. The WHO guidelines for drinking-water quality, 2 µg of uranium per litre, would apply to depleted uranium.

Where possible clean-up operations in conflict impact zones should be undertaken where there are substantial numbers of radioactive particles remaining and depleted uranium contamination levels are deemed unacceptable by qualified experts. Areas with very high concentrations of depleted uranium may need to be cordoned off until they are cleaned up

Since depleted uranium is a mildly radioactive metal, restrictions are needed on the disposal of depleted uranium. There is the possibility that depleted uranium scrap metal could be added to other scrap metals for use in refabricated products. Disposal should conform to appropriate recommendations for use of radioactive materials.

Conclusions: Exposed populations

Limitation on human intake of soluble depleted uranium compounds should be based on a tolerable intake value of 0.5 µg per kg of body weight per day, and that the intake of insoluble depleted uranium compounds should be based on both chemical effects and the radiation dose limits prescribed in the International Basic Safety Standards (BSS) on vi radiation protection. Exposure to depleted uranium should be controlled to the levels recommended for protection against radiological and chemical toxicity outlined in the monograph for both soluble and insoluble depleted uranium compounds.

General screening or monitoring for possible depleted uranium-related health effects in populations living in conflict areas where depleted uranium has been used is not necessary. Individuals who believe they have been exposed to excessive amounts of depleted uranium should consult their medical practitioner for examination, appropriate treatment of any symptoms and follow-up.

Young children could receive greater depleted uranium exposure when playing within a conflict zone because of hand-to-mouth activity that could result in high depleted uranium ingestion from contaminated soil. This type of exposure needs to be monitored and necessary preventative measures taken.

Conclusions: Research

Gaps in knowledge exist and further research is recommended in key areas that would allow better health risk assessments to be made. In particular, studies are needed to clarify our understanding of the extent, reversibility and possible existence of thresholds for kidney damage in people exposed to depleted uranium. Important information could come from studies of populations exposed to naturally elevated concentrations of uranium in drinking water.

vii Depleted uranium: Sources, Exposure and Health Effects

Preface Executive summary Page 1 Introduction 1

2 Sources and properties of depleted uranium and uranium 3 2.1 Uranium 3 2.2 Depleted uranium 6 2.3 Summary 8

3 Uranium in the environment 11 3.1 Air 12 3.2 Water 13 3.3 Soil 15 3.4 Mobility of uranium in soil and water 16 3.5 Food 18 3.6 Other sources in the human diet 19 3.6.1 Cooking and serving containers 19 3.6.2 Uranium in dust and soil 19 3.7 Summary 21

4 Industrial, commercial and military uses of uranium 23 4.1 Historical uses 23 4.2 Current applications 25 4.3 Summary 28

5 Factors influencing routes of intake and exposure 29 5.1 Introduction 29 5.2 Exposure via inhalation 30 5.3 Exposure via ingestion 32 5.3.1 Staple foods 33 5.3.2 Drinking water 36 5.3.3 Soil and dust 37 5.4 Dermal contact 39 5.5 Workplace exposure 40 5.6 Summary 41

6 Case studies and exposure scenarios 43 6.1 Case studies 43 6.1.1 Potential exposure from air crashes 43 6.1.2 Military uses 45 6.2 Environmental exposure scenarios 53 6.2.1 Soil 53 6.2.2 Water 54 6.2.3 Plants 55 6.2.4 Animals 56 6.3 Human exposure scenarios 56 6.4 Summary 59

7 Behaviour of uranium in the body 61 7.1 Introduction 61 7.2 Biodistribution and toxico-kinetics 61 7.3 Ingestion 62 7.4 Inhalation 63 7.5 Injury, insult and dermal sorption 64 7.6 Excretion and elimination 64 7.7 Accumulation 65 7.8 Summary 66

8 The chemical toxicity of uranium 67 8.1 Introduction 67 8.2 Toxicity in experimental animals and humans 68 8.2.1 Experimental animals 68 8.2.2 Implanted depleted uranium fragments 72 8.2.3 Dermal absorption 72 8.2.4 Humans 73 8.3 In-vitro studies 75 8.4 Derivation of a tolerable intake for uranium 76 8.4.1 Soluble uranium compounds 76 8.4.2 Uranium compounds with limited solubility 79 8.4.3 Uranium types practically insoluble in water 79 8.4.4 Other uranium compounds 79 8.5 Uncertainties of chemical risk assessment 79 8.6 Summary 80

9 Health effects due to the presence of radioactivity 81 9.1 Mechanisms and background 81 9.2 Dose limits 83 9.3 External radiation exposure 84 9.4 Internal exposure 85

10 Biokinetics for uranium after internal exposure 87 10.1 Introduction 87 10.2 Inhalation dose coefficients and annual intake limits 87 10.3 Biokinetics of Type F, M and S compounds of uranium after inhalation. 90 10.3.1 Acute exposure 91 10.3.2 Chronic intake 94 10.4 Material specific biokinetic behaviour of inhaled uranium oxides 95 10.4.1 Acute exposure 97 10.4.2 Chronic exposure 101 10.5 Ingestion coefficients and annual intake limits for adult members of the public 103 10.6 Wound contamination 103 10.7 Summary 103

11 Monitoring for internal exposure to depleted uranium 105 11.1 External monitoring of the chest 105 11.2 Urine and faecal monitoring 108 11.2.1 Fluorimetry 109 11.2.2 Alpha spectrometry 109 11.2.3 Mass spectrometry 110 11.3 Wound monitoring 111 11.4 Monitoring for individuals potentially exposed to depleted uranium aerosols. 112 11.5 Monitoring for those with health effects attributed to exposure to depleted uranium 112 11.6 Summary 113

12 Biokinetics of uranium species from the standpoint of nephrotoxicty 115 12.1 Inhalation of uranium. 115 12.2 Ingestion of uranium in drinking water and foods 118 12.3 Relationship between kidney content and urinary excretion 118 12.4 Modelled kidney concentrations resulting from WHO standards. 120 12.4.1 Oral consumption at the TI (soluble compounds) 120 12.4.2 Ingestion at the WHO drinking water guideline value 120 12.4.3 Inhalation at the TI for Type F (soluble) 121 12.4.4 Inhalation at the TI for Type M (moderately soluble) compounds 121 12.4.5 Inhalation at the TI for Type S (insoluble) compounds 121 12.5 Summary 121

13 Protective measures, health monitoring, and medical management 123 13.1 Background information 123 13.1.1 Public exposure 123 13.1.2 Occupational exposure 124 13.2 Protective measures 124 13.2.1 Locality-based protective measures 125 13.2.2 Environment-based protective measures 125 13.2.3 Medical-based protective measures 125 13.2.4 Occupational measures 126 13.3 Preventative actions 127 13.3.1 Air 127 13.3.2 Children 128 13.3.3 Concerned individuals 128 13.3.4 Contaminated items 128 13.3.5 Drinking water 128 13.3.6 Exposed skin 128 13.3.7 Food 128 13.3.8 Impacted areas 128 13.3.9 Metal fragments, depleted uranium munitions, scrap metal and souvenirs 128 13.4 129 13.4.1 Radiation surveys 129 13.4.2 Chemical contamination surveys 129 13.5 Health assessment 129 13.5.1 Medical diagnosis 130 13.5.2 Medical monitoring 132 13.5.3 Treatment of human contamination 133

14 Health standards, guidelines and recommendations 135 14.1 Generic 135 14.2 Drinking water 137 14.3 Food 138 14.4 Soil 138 14.5 Air 139

15 Summary, Conclusions and Research Needs 141 15.1 Summary 141 15.1 Conclusions 147 15.2 Depleted uranium research needs 148

Annex 1 Process of uranium enrichment process 151 Annex 2 Radiological dose due to other nuclides 153 Annex 3 Uranium in the environment, food and reference data 155 Annex 4 ICRP Biokinetic models 165 Annex 5 Chemical toxicity of uranium: Occupational exposure standards after inhalation and the impact of ICRP biokinetic models 175 Annex 6 Methods of chemical and isotopic analysis in support of public health standards and environmental investigations 183

Glossary 187

Bibliography 195